The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Automatic fire protection sprinkler systems are used to protect property and life from damage and loss due to fires. The types of systems that are currently used for fire protection include wet systems that include pressurized liquid throughout the piping system using a system check valve and flow alarm. These systems operate due to heat activation of a fusable heat activated link or glass bulb of the sprinkler allows the release of a plug that permits the flow of liquid or fire suppressant until the sprinkler system is manually shut off.
A dry system is one that flows water when the sprinkler head is opened. A dry system is typically supplied with pressurized air. The water pressure is stopped at the valve by a clapper that is typically held closed by air pressure or a mechanism that is air actuated. When the air pressure is reduced by means of an open sprinkler head, the valve will open and flow water. The size differential ratio for the downstream surface area of the valve member, as compared to the upstream surface area of a dry system valve, is typically in a range between five to one and seven to one, though it could be more per specific standards.
A preaction system is typified by its name. An action must occur before the system is activated. In the case of a single interlocked electric release preaction, a heat detector will trip the valve and release water into the system. Prior to water flowing from the sprinkler system, the sprinkler head must also operate. Likewise, if the sprinkler head operates, the heat detector must still operate before water will flow from the sprinkler system. There are many types of preaction systems. There are non-interlocked (very similar to dry), single interlocked, and double interlocked. The same principle is applied for each one in that there is one or more actions required before water flows from a sprinkler head that has operated. The system in static condition is typically full of air pressure but may also be supervised by another type of medium, such as water, propylene glycol, or nitrogen.
A preaction system that includes supervision of discharge system integrity using air, is typically designed for industrial or commercial applications. Dry preaction systems currently exist in which an air maintenance system provides supervision of the piping system integrity. The benefit of a dry preaction system is that because the piping network is free from water, the risk of pipe freezing is eliminated.
Some dry preaction systems currently available use a flow control valve held closed by system supply liquid pressure. However, these flow control valves require an external check valve, require the removal of a hand-hole cover to reset and latch the valve closed, have a complex design and are large and take up a lot of space. Accordingly, it is desirable in the art to provide a less complex dry and/or dry preaction control valve for a sprinkler system that has an integrated check valve, that is externally resettable, and has a smaller construction.